Draft control



` motor is employed,

Patented Nov. 18, 1941 UN1TED=sTATEs PATENT ori-ICE 2,263,035 i DRAFT CoNTRoL Edward A. Field, Jr., chicago, In. Application February 24, 1941,fse`ria1-N0. 380,095

(o1. 23e-L45) 16 Claims.

This invention relates to improvementA in draft controls.

This is a continuation in part of my copending application Serial No. 332,235, led April 29, 1940, for Draft controls, now Patent No. 2,253,290, dated August 19, 1941.

In the above entitled application there is illustrated and described a novel draft control for stoker-fired or other automatically controlled heating plants adapted to automatically increase `the draft when the furnace or heating plant is in operation, being under the control of the automatic ring or other automatic controlling means; and to substantially diminish the draft.

during the off period of operation, thereby effecting substantial savings in fuel costs. In the operation of that control a stalling motor is employed, the current of which is regulated in accordance with the desired operation, said motor being operatively connected to the draft control gate through a drum and tension chain connected to the gate in such manner that the torque exerted thereon by the motor varies in the manner of an adjustable counterweight mounted on the gate. i

\ In the present application, the main objects are:

First, to provide a draft `control for the foregoing purposes wherein a `uniformly energized Seconc'Lto provide a control of the type `described wherein the variation in the control torque effective on the gate is accomplished by adjusting the point of application ofthe torque thereto `While at the same time insuring that this supplemental torque varies vproportionately with the torque action of a counter-weight on the gate.

Third, to provide a construction ofthe foregoing character which is exceedingly simple and inexpensive in its parts, yet very accurate and sensitive in its action.

Fourth, to provide a control of the type described which is readily embodied in existing furnace installations and which has provision for eliminating mechanical interference of in operation.

'Further objects relating t0 details and'economies of my invention will appear from the description to follow. The invention is dened in the claims.

A structure embodying the features of my invention isillustrated in the accompanying drawing, wherein: p

Fig'. 1 is a fragmentary perspective viewillustratingthe control of my invention in operative 5 to .the art.

its. parts installed relation to a furnace or chimney breeching. e

Fig. 2 is an enlarged fragmentary view in vertical longitudinal section illustrating the draft control housing and gate and other instrumentalities associated therewith for effecting the supplemental control of the gate in accordance with my invention, the motor control drum being arbitrarily shown for the purpose of clarity of illustratlomin a different position from that ordinarilyemployed in practice.

Fig. 3 is a fragmentary view in horizontal section on line 3 3 of Fig. 2, illustrating thegate pivoting structure employed, Y

Fig. 4 is an enlarged fragmentary view illustrating a modified embodiment oi a connection for thesupplemental torque means to the gate operating `in accordance with the principle of the 'present invention.

w Fig. 5 is an enlarged fragmentary view in section on aline corresponding to line `55`of Fig. 4.

- In my application Serial No. 332,235, I describea draft control including a gate having an adjustable counterweight thereon to exert a relatively light gravitational torque on a control gate tendingto close thesame. application included a stalling motor developing a torque variable by relation to the current enerexerted on the gate by the `counterweight due to the gravitational force thereon; Such struc` ture constitutes a control of a very great sensitivity capable of insuring a very low draft during periods of inoperation of the stoker or other firing instrumentality, which, however, is substantially increased vwhen the instrumentality came into operation.

In iaccordance with the present -invention I provide a control motor I enclosed in a suitable housing" 2 secured by a bracket' 3 to the draftA control housing `Il; which `la` .tter is suitably attached to the furnace flue or `chimney `breechng 5 for communication therewith.` Instead of being controlledv by varying the supply current or volt` age therefor, the motor I receives a uniform volt or 220 volt current at all times, being energized when the furnace' rng orfother control device cornes into operation in a manner known During periodslof inoperation of the The control of that ring or control instrumentality, the motor I is deenergized.

In the present structure, the magnitude of the motor torque effective for the desired closing torque supplementary or implementary purpose is determined by the provisions to be described.

The reference numeral 6 designates the draft control gate of the present device, which is pivotally mounted on a trunnion 'I. carried by an adaptor fitting 8 in the mouth of the control housing 4, this tting having the control gate opening 9 therein with which gate 6 coacts to regulate the flow of air into the housing. Though the housing is circular in section, the opening is truncated at its sides by the provision of rearwardly extending wings II) on fitting 8 and it will be understood that the gate is similarly truncated at its sides. The control housing open# ing is thus generally rectangular in outline.

The gate 6 is provided with a counterweight or balance mechanism consisting Aj of the rear weight IIy attached to the inner side thereof and a further front yadjustable counterweight I2 secured to an elongated forwardly vextending rod I3 attached to the gate in line with weight II. The counterweight I2 is manually adjustable on rod I3 and secured thereon byv a setscrew I4 or, alternatively, the counterweight may be adjustably threaded on the rod Afor positioning so that the counterbalance mechanism as a whole exerts a closing torque on` the gate, being, however, preferably resistant, only to a very light draft pressure. Thus, the draft during the off period might be only .02 or .03 inch, or only slightly more than a zero draft setting. Alternatively the net counterbalancing torque by such means could in somey installations be operative in the other direction. When the burner or other combustion or control instrumentality for the heating plant cornes into operation, it is intended that the draft in the control housing be increased substantially and to anyextent necessary, and to this endl provide the supplemental connections to the controlrmotor I to be described to thereby variably increase the closing torque on `the gate during on operation. .These supplemental provisionsvconsist of a plate-like arm or bracket I secured to and projecting from the front side of the gate and pro,-y vided witha row of apertures Iii for the recepf tion of a wire,n rod-like tension connector I'I. This connector is secured at its other end to a flexible tension member or chain I8 wound on the drumISon motor I. .n v Y It will beA appreciated that in practice the counterbalance vweight I2 is properlypositioned on rod .I3 having regard forthe dead weight of connector Il and chain I81which are supported by thegate when vthe motor is `not energized. In other Words, the net or. resultant of all the gravitational forces exerting 4torque on the gate is preferably suchl that a slight Closing tendency is imparted thereto during off periods of the firingork control instrumentality, though the opposite is possible, so long as closing torque is applied by the motorized means ,during the on periods, such that vthe total eiect on the gate is, Vin the closing direction.

It will be noted with ,reference to` Fig. 2, Aand it is of essential importance in the present inventiomthatthe holes I6 are arranged along an arcuate or curved line. It is evident that the supplemental torque exerted -on the gate by the motor I through theconnector l'I .will Vary lin magnitude in accordance Ywith which hole the connector rod II is engaged, for the length of the moment arm or torque arm of the force is thereby determined. Were the holes I6 arranged in a straight line, however, a variable would be introduced because of the different angle deiined by theoretical lines extending respectively from the centers of two different holes to the gate pivot point I and from the center of the hole tangent to drum I9, the latter line being the line of force of the motor. The holes are therefore arranged in a curvilinear row or outline to compensate for and eliminate this variable factor. Thus it will be noted with reference to Fig. 2 that when the connector I'I is attached to the extreme end hole, the angle A is enclosed by a theoretical line from the center of the said extreme hole and the pivot I and by the line of force through the hole tangent to the drum. The line of force obviously is merely an extension of the center line of tension chain I8. Were the connector I1 inserted or attached in a hole, say ve places further to the right in Fig. 2, the corresponding angle would be as shown and indicated by the character B. By reason of the curved disposition of the holes in the present device, angles A and B are equal, so that for any point of attachment of the motorized control to the gate arm I5 the supplemental torque on the gate, regardless of its amount, varies in the same manner due to angularity introduced in the operation of the gate.

The connector II is preferably offset rearwardly at 20 so as to clear the lower edge of the gate as the latter swings outwardly, for example, as illustrated in dotted lines in Fig. 2. A hook 2l is provided at the end of the offset in this connector for engagement with the holes I8. It will be understood that this special conguration of the connector I1 has no eiect on the force exerted on the gate, which is the same as if a tensioning element, ilexible or straight in its entirety, were employed. This hook may be readily twisted and removed from any given hole l'for connection with another.

For the purpose of ease of illustration and to clarify the foregoing angular relationships, I have chosen to show the motor positioned with its axis parallel tothe axis of the gate. However in practice it may be desirable to arrange the motor axis at ninety degrees of this position, in the manner shown in the above identied application.. Such a disposition enables a self compensating travel of the tension chain on the motor drum to thereby minimize the tendency to .depart from an exactly vertical pull. Provisions to this end are shown and described in said copending application.

The foregoing control is a very simple and inexpensive one and highly eiective in operation. The torque for the gate varies in the same proportionate manner for the various gate positions, regardless of which hole the connector or link II is engaged with, being of course stronger when the latter is in a hole nearer the outer end of the gate. l

As illustrated in solid lines in Fig. 2, the theoretical line X-Y drawn through the gate pivot and the point of attachment of the motor tensioned element II is approximately parallel to the axis of counterweight rod I3, hence the concept disclosed in my application Serial No. 332,235 of maintaining the variations in torque exerted by the motor proportional to the counterweight torque, regardless of the angular position of .the gate, is also embodied in this application. However, when connector Il is attached to another ofthe holes I6, `as for example the sixth hole from the left in Fig; 2, then L-M would be the theoretical line through said hole and the gate axis. This is evidently not parallel to the axis of rod I3, so that in this respect there i isv apparentlya slight departure from the principle relied on: in i my `aforesaid application. However, in practice the curvature of the row of holes may be less ,pronounced than as illustrated so as to achieve a balance between the factors of (a) approximate, if not exact, equivalency of the angles A, B; and (b) approximate, if not exact, parallelism of line L-M or X-Y with the counterweight .rod I3. Thus to a great extent the fruits of both concepts may be secured. Wherever positioned, connector Il will closely simulate in proportion the variations in the `counterweight torque in the operation of the gate, and likewise the. motor will be eifective onthe latter, throughout the swing ofthe gate and with the connector inf` one hole I6, in a manner closely approximating its action in another hole, though of course quantitatively different. From the foregoing, it will be appreciated that in all cases the line of force exerted by the motor and corresponding to the centerline of the chain is at the same angle to a line extending from the axis or pivot of the gate to the hole in which the link Il is attached. Practical `experience in operation has indicated that this angle, marked A or B in Fig. 2, should be somewhere between 110 and 115. Accordingly rod I3 is arranged to` extend downward at a similar angle. Hence the torque produced by the power of the motor and applied to the gate has the same effect thereonfas that produced by the counterweight I2.` The gravitational force on the counterweight `I2 acts vertically, but the power of the motor can be applied in quite a number of directions and still be similar in its variation in effect to that of the counterweight. This adjustable connection of the motor to the gate considerably reduces the cost of the control.v No rheostat or ,other current control means are required and the special gate arm and motor connector can be supplied atlittle cost. In Figs. 4 land 5, I illustrate a slightly modified embodiment of the means for attaching the motor connector link to the gate, the link in this instance being indicated by the reference numeral 22. In this embodiment, a forwardly and downwardly curved arm or bracket 23 is secured to the gate 24 in any suitable manner, being provided with a similarly curved or arcuate slot 25. Adjustable in this slot is a headed clamp screw 26 through which an offset 21 of the link extends longitudinally, being maintained against separation by a cotter pin 28. Screw 26 threadedly receives ythe-clamp nut 29 for securing the link in any desired position in the slot 25,` it being understood that `the link offset is freely pivotal in the axial opening in the screw receiving the same.

, `Ihave illustrated and described my improvements in embodiments which are very practical. I have not attempted to illustrate or describe other embodiments `or adaptations as it `is believed this disclosure will enable those skilled in the art to embody or adapt my improvements as may be desired.

i Having thus` described` my invention, what I Patent is: A

1. A draft control for an automatically fired furnace or boiler controlled by an automatic instrumentality, comprising a motor governed by said instrumentality,` an open ended control housing Acommunicating with the flue of the furnacev or boiler andhaving a gate pivotally mounted thereon adjacent the opening to control theflow of air through the latter, a counterweight adjustably mounted on a downwardly extending arm secured to said gate, said counterweight normally exerting a relatively slight torque on the gate tending to swing the same toward closing position, and a supplemental torque applying bracketsecured on and projecting outwardly from said gateand provided withva series of apertures arranged in 'a downwardly andA outwardly curved4 outline, said motor having a winding drum-provided with a flexible connector having removable and selective connection with vone of said apertures whereby to regulate the amount of torque supplementary to the torque `of said counterweightwhich is applied to the gate by said motor and connector, the curvature vof said series of apertures being such that the line of force from theimotor to any one thereof is at a predetermined substantially constant angle to a i line from said aperture to the pivot of the gate, said counterweight supporting rod being arranged on said gate' at a similar angle.

2. A draft control for an automatically fired furnace or boiler controlled by an automatic instrumentality, comprising a motor governed by said instrumentality, an open ended control housingacommunicating with the flue of the furnace or boiler and having a gate pivotally mounted thereonadjacent the opening to control the flow of air` through the latter, a counterweight adjustably mounted on an arm secured to said gate, said counterweight normally exerting a relatively slight torque on the gate tending to swing the same toward closing position, and a supplemental torque applying bracket secured on'and projecting outwardly from said gate and provided `with a series of apertures arranged in a downwardly and outwardly curved outline, said` motor having a connector having removable and selective connection with one of said apertures whereby to regulate the amount of torque supplementary tothe torque of said counterweight which is applied to the gate by said motor and connector, the curvature of said series of apertures being such that the line of force from the motor to any one `thereof is at a predetermined substantially constant angle to a line from said aperture to the pivot of the l gate, said counterweight supporting rod being arranged on said gate at a similar angle.

3. A vdraft control for an automatically fired furnace or boiler controlled by an automatic instrumentality, comprising a motor governed by said instrumentality, an open ended control housing communicating with the nue of the furnace or boiler vand having a gate pivotally mounted thereon adjacent the opening to control the flow of air through the latter, a counterweight adjustably mounted on an arm secured to said gate, said counterweight normally exerting a relatively slight torque on the gate, and a supplemental torque applying bracket secured on and projecting outwardly from said gate and vprovided with a series of apertures arranged in acurved outline, said motor having a connector having removable and selective connection with one of said apertures whereby to regulate the amountof torquesupplementary to the torque of said counterweight which is applied to the gate by said motor and connector, the curvature of said series of apertures being such that the line of force from the motor to any one thereof is at a predetermined substantially constant angle to a line from said aperture to the pivot of the gate. f

4. A draft control for an automaticallyred furnace or boiler controlled by an automatic instrumentality, comprising a motor governed by said instrumentality, an open ended control housing communicating with the nue of the furnace or boiler and having a gate pivotally mounted thereon adjacent the opening to control the ow of air through the latter, and a torque applying bracket secured on and projecting outwardly from said gate and provided with a-series of apertures arranged in a curved outline, said motor having a connector having removable and selective connection with one of said apertures whereby to regulate the amount `of torque applied to the gate by said motor and connector, the curvature of said series of apertures being such that the line of force from the motor to any one thereof is at a predetermined substantially constant angle to a line from said aperture to the pivot of the gate.

5. A draft control for an automatically fired furnace or boiler controlled by an automatic instrumentality, comprising a motor governed in its operation by said instrumentality, a control housing communicating with the flue of the furnace or boiler and having an opening and a gate pivo-tally mounted thereon adjacent the opening to control the flow of air through the latter, a

counterweight adjustably mounted on a downwardly extending arm secured to said gate, said counterweight normally exerting a relatively lslight torque on the gate tending to swing the same toward closing position, and a supplemental torque applying bracket projecting outwardly from said gate and apertured along a curved outwardly and downwardly extending line to adjustably receive a connector, said motor having a winding drum provided with a flexible connector having means for removable and selective connection with said gate bracket at the'apertured` portion thereof to regulate the amount of torque supplementary to the torque of said counterweight which is applied to the gate by said motor and connector, the curvature of said apertured line being suchv that the line of for-ce from the motor to any desired point thereon is at a predetermined constant angle to a line from said one to the pivot of the gate, said counterweight supporting rod being arranged on said gate at a similar angle.

6. A draft control for an automatically red furnace or boiler controlled by an automatic instrumentality, comprising a motor governed in its operation by said instrumentality, a control housing communicating with the flue of the furnace or boiler and having an opening and a gate pivotally mounted thereon adjacent the opening to control the ow of air through the latter, a counterweight adjustably mounted on a downwardly extending arm secured to said gate, said counterweight normally exerting a relatively slight torque on the gate, and a supplemental torque applying bracket projecting outwardly from said gate and apertured along a curved line to adjustably receive a connector, said motor having a winding drum provided with a connector having means for removable and selective connection with said gate bracket at the apertured portion thereof to regulate the amount of torque supplementary to the torque of said counterweight which is applied to the gate by said motor and connector, the curvature of said apertured line being such that the line of force from the motor to anydesired point thereon is at a predetermined constant angle to aline from said one tothe pivot of the gate, said counterweight supporting -rod being arranged on said gate at a similar angle.

7. A draft control for an automatically red furnace or boiler controlled by an automatic instrumentality, comprising a motor governed in its operation by said instrumentality, a control housing communicating with the flue of the furnace or boiler and having an opening and a gate pivotally mounted thereon adjacent the opening to control the flow of air through the latter, and a torque applying bracket projecting outwardly from said gate and apertured along a curved line to adjustably receive a. connector, said motor having a winding drum provided with a connector having means for removable and selective connection with said gate bracket at the apertured portion thereof to regulate the amount of torque applied to the gate by said motor and connector, the curvature of said apertured line being such that the line of force from the motor to any desired point thereon is at a predetermined constant angle to a line from said one 'to the pivot of the gate.

8. A draft control for an automatically fired furnace or boiler controlled by an automatic instrumentality, comprising a motor governed in its operation by said instrumentality, a control housing communicating with the flue of the furnace or boiler and having an opening and a gate pivotally mounted thereon adjacent the opening to control the ilow of air through the latter, a torque applying bracket projecting outwardly fromv said gate and apertured along a curved line to adjustably receive a connector, and a motor connector connected to said motor having means for removable and selective connection with said gate bracket at the apertured portion thereof to regulate the amount of torque applied to the gate by said motor and connector, the curvature of said apertured line being such that the line of force from the moto-r to any desired point thereon is at a predetermined constant angle to a line from said one to the pivot of the gate.

'9. A motorized draft control for an intermittentlyoperating furnace or boiler controlled by an automatically operated instrumentality, comprising a control housing communicating with the flue of the furnace or boiler and having a swinging control gate pivotally mounted therein, counterweight means associated with said gate including an adjustable counterbalance and effective to exert a slight torque on the gate tending to swing the same to closing position, and means for supplementing the action of said counterweight means at certain periods, cornprising a'motor controlled by said instrumentality to come into operation when said instrumentality is operated, said motor having an actuating drum thereon, an outwardly extending bracket on said gate, and flexible tensioning means associated with and actuated by the motor drum and provided with a link connector having an outward offset therein to accommodate said gate in the swinging thereof, said connector being removably attachable to said bracket and the latter having curvedly disposed means for the selective reception `of said` connector at varying distances from the gate pivot, whereby toprovidedifferent, moment arms for'l the application of motor torque and `whereby `the line of force of the motor isat a predetermined constant angle to a line between the point of attachment of the connector and the pivot of the gate, regardless of the moment larm of the torque.

10. A motorized draft control for an intermittently operating furnace or' boiler controlled by an automatically operated instrumentality, comprising a control housing. communicating with the ilue of the furnace or boiler and having a control gate pivotally mounted therein, counterweight means associated with said gate including an adjustable counterbalance and effective to exert a slight torque on the gate tending to swing the same to closing position, and means for supplementing the action of said counteri weightmeans at certain periods, comprising a motor` controlled by said instrumentality to come into operation when said instrumentality is operated, said motor having an actuating drum thereon, an outwardly extending bracket on said gate, and flexible tensioning means associated with and actuated by the motor drum and provided with a connector, said connector being removably attachable to said bracket and the latter having curvedly disposed means for the selective reception of said connector at varying distances from the gate pivot, whereby to provide different moment arms for the application of motor torque and whereby the line of force of the motor is at a predetermined'constant angle to a line between fective to exert a slight torque on the gate tending to swing the same to closing position, and means for supplementing the action of said counterweight means at certain periods, comprising a motor controlled by said instrumentality to come into operation when said instrumentality is operated, a bracket on said gate, and tensioning means associated with and actuated by the motor and provided with` a connector, said connector being removably attachable to said bracket and the latter having curvedly disposed means for the selective reception of said connector at varying distances from the gate pivot, whereby to provide different moment arms for the application of motor torque and whereby the line of force of the motor is at a predetermined constant angle to a line between the point of attachment of the connector and the pivot of the gate, regardless of the moment arm of the torque.

12. A motorized draft control for an inter- `mittently operating furnace or boiler controlled by an automatically operated instrumentality, comprising a control housing communicating with the flue of the furnace or boiler and having a control gate pivotally mounted therein, counterweight means associated with said gate eifective to exert a torque on the gate tending to swing the same, and means for the action of said counterweight means at certain periods,

, comprising a motor controlled by said instrumentality to come into operation when said instrumenta'lity` is operated, -a'bralcket on said gate, and tensioning means associated with and actuated by themotor and provided with a connector, said connector being removably attachable to said bracket and the latter having curvedly disposed means for the selective reception of said connector at varying distances from the gate pivot, whereby to provide different moment arms for the application of motor torqueand -whereby theline of force of the motor is at a predetermined constant angle to a line between the point of attachment of the connector and the pivot of the gate,` regardless of the moment arm of the torque.

13. A motorized draft control for an intermittently operating furnace or boiler controlled by an automatically operated instrumentality, comprising a control housing communicating with the flue of the furnace or boiler and having a control gate pivotally mounted therein, counterweight means associated with said gate, and means for implementing the action of said counterweight means, comprising a motor controlled by said instrumentality to come into operation when said instrumentality is operated, said moto having an actuating drum thereon, a bracket on said gate, and flexible tensioningmeans associated with and actuated by the motor drum and provided with a connector removably attachable to said bracket, the latter` having curvedly disposed meansfor the selective reception of said connector at varying distances from the gate pivot whereby to provide different moment arms vfor the application of motor torque and whereby the line of force of the motor is at a predetermined constant angle to a line between the point of attachment of the connector and the pivot of the gate, regardless of the moment of the torque.

14. A motorized draft control for an intermittently operating furnace or boiler controlled by an automatically operated instrumentality, comprising a control housing communicating with the flue of the furnace or boiler and having a control gate pivotally mounted therein, a motor controlled by said instrumentality to come into operation when said instrumentality is operated, said motor having an actuating drum thereon, a bracket on said gate, and flexible tensioning means associated with and actuated by the motor drum and provided with a connector removably attachable to said bracket, the latter having curvedly disposed means for the selective reception of said connector at varying distances from the gate pivot whereby to provide different moment arms for the application of motor torque and whereby the line of force of the motor is at a predetermined constant angle to a line between the point of attachment of the connector and the pivot of the gate, regardless of the moment ofthe torque. l

l5. A motorized draft control for an intermittently operating furnace or boiler controlled by an automatically operated instrumentality, comprising a control housing communicating with the flue of the furnace or boiler and having a control gate pivotally mounted therein, a motor controlled by said instrumentality to come into operation when said instrumentality is operated, a bracket on said gate, and means associated with and actuated by the motor including a connector removably attachable to said e bracket, the latter having curvedly disposed means for the selective reception of said connector at varying distances from the gate pivot whereby to provide different moment arms for the application of motor torque and whereby the line of force of the motor is at a predetermined constant angle to a line between the point of attachment of the connector andthe pivot of the gate, Vregardless of the moment of the torque.

1.6. In a draft control of the type described, a control housing having a gate pivotallyvmounted thereon, the lower edge of said gate being swing- 10 able substantially outwardly in the operation thereof, a motorized control for the gate including a motor having a exible actuating element, and a link connector from said element to a bracket on the front of the gate, said link connector being disposed in front of said gate and having a substantial offset therein to receive and accommodate the lower edge of said gate in said outward swinging movement of the latter.

EDWARD A. FIELD, Jn. 

